discourse/db/post_migrate/20220825005115_backfill_outbound_message_id.rb
Martin Brennan e3d495850d
FEATURE: Overhaul email threading (#17996)
See https://meta.discourse.org/t/discourse-email-messages-are-incorrectly-threaded/233499
for thorough reasoning.

This commit changes how we generate Message-IDs and do email
threading for emails sent from Discourse. The main changes are
as follows:

* Introduce an outbound_message_id column on Post that
  is either a) filled with a Discourse-generated Message-ID
  the first time that post is used for an outbound email
  or b) filled with an original Message-ID from an external
  mail client or service if the post was created from an
  incoming email.
* Change Discourse-generated Message-IDs to be more consistent
  and static, in the format `discourse/post/:post_id@:host`
* Do not send References or In-Reply-To headers for emails sent
  for the OP of topics.
* Make sure that In-Reply-To is filled with either a) the OP's
  Message-ID if the post is not a direct reply or b) the parent
  post's Message-ID
* Make sure that In-Reply-To has all referenced post's Message-IDs
* Make sure that References is filled with a chain of Message-IDs
  from the OP down to the parent post of the new post.

We also are keeping X-Discourse-Post-Id and X-Discourse-Topic-Id,
headers that we previously removed, for easier visual debugging
of outbound emails.

Finally, we backfill the `outbound_message_id` for posts that have
a linked `IncomingEmail` record, using the `message_id` of that record.
We do not need to do that for posts that don't have an incoming email
since they are backfilled at runtime if `outbound_message_id` is missing.
2022-09-26 09:14:24 +10:00

26 lines
762 B
Ruby

# frozen_string_literal: true
class BackfillOutboundMessageId < ActiveRecord::Migration[7.0]
def up
# best effort backfill, we don't care about years worth of message_id
# preservation
#
# we also don't need to backfill outbound_message_id for posts that
# do _not_ have an incoming email linked, since that will be backfilled
# at runtime if it is missing
sql_query = <<~SQL
UPDATE posts
SET outbound_message_id = ie.message_id
FROM incoming_emails AS ie
WHERE ie.post_id = posts.id
AND posts.created_at >= :one_year_ago
AND posts.outbound_message_id IS NULL
SQL
DB.exec(sql_query, one_year_ago: 1.year.ago)
end
def down
raise ActiveRecord::IrreversibleMigration
end
end